The Introduction Arc is the first arc of the Hedgehog Piece series and East Blue Saga. This arc involves is basically the introductions of several characters and crews.
The ThunderScar's story begins with Nitro V. Kaian, having recently escaped Marine captivity and having stolen one of their ships, being confronted by another Marine ship, this one headed by Gale Walker
Nitro: Fights his way through the Marines until Commander Walker punches him through their ship, sending him into a prison's cell. That prisoner is none other than Dark Ranoki, whom he convinces to join his crew. The two then fight against the Marines together. Nitro is ultimately left alone to fight against Commander Walker, whom he defeats after a bit of struggle.
Dark: After Nitro frees him, the two begin to fight against Marines. As he's fighting, Max Hedgedroid comes to his assistence and the two begin to wreck havoc on the weaker, grunt Marines. After they've defeated them all, they wait while Nitro faces Commander Walker.
After Nitro's win, the ThunderScars, and Max, are confronted by Admiral Pacifista Alpha. After getting over the shock, Nitro causes a quick distraction by shooting electricity into the sky, causing lightning to strike down and destroy the ship. After using his LightSpeed Warp to get away, the three discover Viu E. Blaze on their ship. They have quick introductions before sailing away. However, they aren't safe as another Marine ship is hightailing them, this one lead by Captain Fritz E. Kriegs. After launching himself onboard, they talk for a bit before Viu apparently activates his Devil's Fruit. Unforunately, before he can do anything, Lieutenant Blixx Nova takes Fritz and Nitro away. After a little more talking, Max uses his Devil's Fruit ability to bring Nitro back onto their ship and sail away, though unforunately, their rudder is broken and they'll simply drift towards Raven's Point.
The story of this unnamed group of pirates actually starts with someone who is not the captain of the, for now, yet to be unnamed crew. It starts with Frost Shinekuya attacking an entire ship of Marines, specifically the Punishment Branch led by Fritz E. Kriegs. Frost: He is introduced into the series when attacking the Punishment Branch by using his Devil's Fruit to freeze the entire ship. To his dismay, Fritz is left stranded in the ocean after hopping off the ship before it had been frozen by Frost and is then confronted by him. Frost questions Fritz about the massacre that occured at Raven's Point, is home island. Fritz quickly escapes Frost's grasp using Rokushiki so Frost goes on his way. While doing so, he runs into a Marine cargo ship that doesn't exactly hold anyone on board so he goes to the lower decks to investigate.
Anise: Little Anise S. Divine awakes on a ship, not exactly knowing what is going on or how she got there and feeling a bit dizzy as the boat rumbles. Confused and scared she ponders about where she is, when suddenly she hears noises from others and she questions what they are doing and why are they holding her. Afraid, she tries to calm herself by concentrating and pleaing for someone to help her.
It is then that Frost comes in and saves Anise from the Marines and liberates her from their custody. Although, not official, Frost decides to stay with Anise as a group to watch over her as she is still a kid. Even though he really did not want to. All the while, they take over the cargo ship. In another location, with an unseen individual, it is shown that both Frost and Anise are going through the finalization of there bounties and will soon be dubbed as criminals.
Toadi: All the while, Toadi Firma is introduced awakening on an island that he had been stuck on, thinking of a few things that has occured to him and what he should do to get off the island. He finally decides to start building a bridge with his Devil's Fruit to try and get to another island far away. While doing so, he bumps into the Marine cargo ship that Anise and Frost had been on and stays with them after thanking them for getting him off of the island. While thanking them, he pauses mid-thanks to acknowledge Anise and comment her looks by calling her an angel from heaven. After a bit of dialouge between the now three, Anise lets Toadi stay on the ship until they reach the next island.
Afterwards, Anise asks where they should go next and Frost demands that they go to Raven's Point for two reasons. One because of a wreckage there that could help them out with their ship and gather supplies and the second had been more personal for Frost that he did not want to share. Anise nor Toadi speak up against the matter, so they set sail after a bit of disruption between the group and head towards Raven's Point.
Blitz: After setting their destination, their story pans over to a lost individual, Blitz Talon, whom is lost at sea in search of an island or ship that could help him out. Once he sees the Marine cargo ship that holds the group, he uses his water vehicle to speed towards them and crash right into the ship. He goes up to greet everyone else, where the group disputes and yells over each other about him causing a hole in their ship that'll eventually cause the ship to sink. After a while, they shrug it off and worry about heading to their next location.
The story of The Ouroboros starts with, Yonko Silas A. Bourne riding through the East Blue on an uncanny and small motorized mechanical boat. He comes near a ship of Marines that plan on attacking Nitro and Dark from afar after they saw that the other ship of Marines led by Commander Walker were attacked by them. Silas, for some reason, stops them by using a mysterious ability to slash right through the entire ship using a strange energy and proceeding on towards his destination.